1. Field of the Invention
The present invention relates to the field of integrated optical components, and more specifically to passive integrated optical components for coupling integrated waveguides, such as polarization splitters, filters, and intensity splitters.
2. Discussion of Prior Art
As illustrated in FIG. 1, a polarization splitter is a device 1 to which are associated an input waveguide 2 and two output waveguides 3 and 4, one of the output guides possibly being an extension of the input guide. This device is intended to extract, from an input waveguide containing transverse electric (TE) and transverse magnetic (TM) modes, at least part of one of the polarization modes, for example, the TM mode in the case shown in FIG. 1.
An example of an integrated polarization splitter which is not associated with waveguides is illustrated in FIG. 2. This polarization splitter is for example described in a paper by Junming Zhao et al. published in Applied Physics Letters 92, 071114 (2008). An incident beam 11 arrives under oblique incidence on the edge of a succession of parallel metal strips 12 formed in an insulating material, and the paper discloses that, for a proper sizing, a reflected beam 13 containing the TE polarization component and a transmitted beam 14 containing the TM polarization of the beam are obtained.
Further, in the field of optical integrated circuits, where waves propagate within waveguides formed inside or on top of a support material, various other types of polarization splitters separating the TE and TM components of the wave carried by an input waveguide between the continuation of this waveguide and another waveguide have been developed, for example, Y-shaped structures or photonic crystal structures.
However, known structures have the disadvantage that the surface necessary for the polarization splitting is relatively large, currently with a length ranging from 10 to 100 times the wavelength of the light which propagates in the waveguides. Further, such structures are often complicated to manufacture and require an extremely accurate sizing of their elements.